The invention relates to a charge-coupled device (CCD) comprising a monocrystalline semiconductor body having a layer-shaped region of the one conductivity type, which adjoins a major surface and is provided with: a charge transport channel for storing and transporting supplied information in the form of charge packets; electrical connection means for applying a voltage V.sub.BB to the layer-shaped region; an input circuit comprising a zone (designated as an input diode) of the second conductivity type; and supply means for supplying a signal-dependent voltage to the input diode.
Charge-coupled devices, in which the input signal is supplied as a voltage to the input diode, are generally known. When a suitable voltage is applied to the first storage-electrode (input gate), a potential well is induced in the channel which can be filled with a charge packet. There is arranged between the input diode and the first storage electrode, a sampling gate, by means of which the input diode and the said charge packet can be connected to each other and can be insulated from each other. The size of the charge packet depends upon the potential of the input diode and hence upon the input signal. In general, the zero level, at least with surface CCD's, is chosen so that even with a "0" input signal a certain amount of charge is introduced into the said potential well (fat zero or reference charge). The maximum level depends upon the depth of the potential well. When the charge packet and the input diode are insulated from each other, the charge packet can be transported further, for example, by applying to the next subsequent clock electrode, a sufficiently high voltage, as a result of which there is formed under this clock electrode a deeper potential well which receives the charge packet.
It has been found in practice that with such an input circuit unexpectedly large distortions of the signals frequently occur. These distortions may even be so large that, for example, with digital information, in which event only a "0" level and a "1" level (full bucket) are present, it is difficult to discriminate these levels from each other at the output because the "0" level (empty bucket) has filled substantially completely. These distortions especially occur in charge-coupled devices in which the clock electrodes comprise a transfer part and a storage part, means being internally provided, such as a difference in doping concentration or a difference in oxide thickness, to generate a difference in threshold voltage. Such an electrode configuration occurs, for example, in a two-phase CCD, in which a potential barrier with respect to the storage part should be formed under the transfer part. Due to this asymmetrical configuration, it is achieved, as is well known, that charge transport can take place in only one direction.